To solve the problem of a conventional cushion material for mattress wherein the part for laying a person is gradually deformed to form a difference in height between the center part and peripheral part of the mattress, which deteriorates the comfortableness to sleep, to provide a cushion material for mattress free from sense of bottoming, excellent in moisture permeability and air permeability with satisfactory cushioning property, simplified in manufacturing process, and never deformed even by a long-term use.

This cushion material for mattress is formed of a three- dimensionally knitted fabric formed by connecting a surface knitted fabric and a lining knitted fabric through a connecting yarn. The knitting density is changed in multi-stages according to using positions to provide hardnesses suitable to the using positions.